All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Jews, Christians, Buddhists, or people who embrace any religion other than Islam are considered disbelievers. Considering them disbelievers is one of the indisputably established facts of Islam. Anyone who rejects, denies or doubts this is considered a disbeliever, as this contradicts their faith.
Al-Qaadhi ‘Iyaadh who followed the Maaliki school, said that any Muslim who thinks that any other religion is true or doubts the invalidity of any other religion is considered a disbeliever by consensus.
Shaykh Al-Hajjaawi who followed the Hanbali School, said that anyone who does not consider Christians and Jews to be disbelievers or doubts this is a disbeliever himself. This is because he is denying the verse where Allaah The Almighty Says (what means):
• {And whoever desires other than Islam as religion - never will it be accepted from him, and he, in the Hereafter, will be among the losers.} [Quran 3:85]
Allaah Knows best.